1. Field of the Invention
The present invention generally relates to magneto-resistive effect type (hereinafter simply referred to as magneto-resistive) heads and magnetic recording and reproducing apparatuses, and more particularly to a magneto-resistive head which uses a stabilizing bias layer to apply a magnetization stabilizing bias field on a magneto-resistive layer, and to a magnetic recording and reproducing apparatus which is provided with such a magneto-resistive head.
2. Description of the Related Art
FIG. 1 is a cross sectional view showing an important part of a conventional magneto-resistive head. As shown in FIG. 1, the conventional magneto-resistive head has a rectangular magneto-resistive element (spin valve element) 1 connected to element terminals 3, and the top and bottom of the magneto-resistive element 1 and the element terminals 3 are respectively insulated by alumina (Al2O3) layers 4 and 5. In addition, two soft magnetic layers (not shown) made of a soft magnetic material such as NiFe respectively shield the top of the alumina layer 4 and the bottom of the alumina layer 5.
The reproducing element is provided with vertical bias applying layers 7 for stabilizing the reproduced output, and a hard magnetic material is used for the vertical bias applying layers 7. It is known that the hard magnetic characteristic can be improved by using a thin film having a bcc crystal structure for an underlayer of the hard magnetic material.
For example, a Japanese Laid-Open Patent Application No. 9-97409 proposes improving the stabilization of the reproduced output by using the thin film having the bcc crystal structure for the underlayer of the hard magnetic material. It is regarded that the improved stabilization of the reproduced output is achieved by the transfer coupling of the ferromagnetic material such as Fe and a free layer of the spin valve element. For example, in a case where CoCrPt is used as the hard magnetic material with respect to the underlayer which is made of Fe with a thickness of 10 nm or made of FeCr with a thickness of 10 nm, the magnetic field becomes 1000 to 1200 Oe, and it is possible to effectively suppress the Barkhausen noise.
The specific resistance of CoCrPt which is used as the hard magnetic material is 60 to 80 xcexcxcexa9cm and is high. For this reason, there was a problem in that the resistance of the magneto-resistive head as a whole becomes large, thereby causing head noise (white noise) and deteriorating the head characteristic.
In addition, the residual magnetization of CoCrPt which is used as the hard magnetic material is low, and it is necessary to increase the film thickness in order to obtain a sufficiently satisfactory head characteristic. However, when the film thickness of the hard magnetic material is large, there was a problem in that undulations are formed in the write head, thereby deteriorating the recording and reproducing characteristic.
Furthermore, in a case where CoPt which has a high magnetic flux density is used as the hard magnetic material and the ferromagnetic underlayer having the bcc crystal structure as proposed in the Japanese Laid-Open Patent Application No. 9-97409 is used, there was a problem in that it is difficult to obtain a satisfactory hard magnetic characteristic, as may be seen from FIG. 2. FIG. 2 is a diagram showing the characteristic of the ferromagnetic underlayer having the bcc crystal structure, for a case where the thickness of the Fe layer is 3 nm and the thickness of the CoPt layer is 10 nm. In FIG. 2, the ordinate indicates the magnetization in Gauss, and the abscissa indicates the magnetic field in Oe.
Accordingly, it is a general object of the present invention to provide a novel and useful magneto-resistive head and magnetic recording and reproducing apparatus, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a magneto-resistive head and magnetic recording and reproducing apparatus, which can reduce the head noise and obtain a satisfactory head characteristic, prevent deterioration of the recording and reproducing characteristic by preventing undulations from being formed in the write head, so that a satisfactory hard magnetic characteristic can be obtained.
Still another object of the present invention is to provide a magneto-resistive head comprising a stabilizing bias layer which applies a magnetization stabilizing bias field on a magneto-resistive layer of a magneto-resistive element, and a ferromagnetic underlayer which forms an underlayer with respect to the stabilizing bias layer, where the ferromagnetic underlayer is made of Fe and has a film thickness in a range of 1.3 to 2.5 nm. According to the magneto-resistive head of the present invention, it is possible to reduce the head noise and obtain a satisfactory head characteristic, and to prevent undulations from being generated in the write head so as to prevent deterioration of the recording and reproducing characteristics, and it is possible to obtain a satisfactory hard magnetic characteristic.
A further object of the present invention is to provide a magneto-resistive head comprising a stabilizing bias layer which applies a magnetization stabilizing bias field on a magneto-resistive layer of a magneto-resistive element, and a ferromagnetic underlayer which forms an underlayer with respect to the stabilizing bias layer, where the ferromagnetic underlayer is made of a Fe-based alloy which is added with at least one element selected from a group of Co, Ni, Cr, Nb, Mo, Ta, V and W, and has a film thickness in a range of 2.5 to 4.9 nm. According to the magneto-resistive head of the present invention, it is possible to reduce the head noise and obtain a satisfactory head characteristic, and to prevent undulations from being generated in the write head so as to prevent deterioration of the recording and reproducing characteristics, and it is possible to obtain a satisfactory hard magnetic characteristic.
Another object of the present invention is to provide a magneto-resistive head comprising a stabilizing bias layer which applies a magnetization stabilizing bias field on a magneto-resistive layer of a magneto-resistive element, and a ferromagnetic underlayer which forms an underlayer with respect to the stabilizing bias layer, where the ferromagnetic underlayer is made of a Fe-based alloy which is added with at least one element selected from a group of Pt, Pd, Ir, Rh, Ru and Au. According to the magneto-resistive head of the present invention, it is possible to reduce the head noise and obtain a satisfactory head characteristic, and to prevent undulations from being generated in the write head so as to prevent deterioration of the recording and reproducing characteristics, and it is possible to obtain a satisfactory hard magnetic characteristic.
Still another object of the present invention is to provide a magneto-resistive head comprising a stabilizing bias layer which applies a magnetization stabilizing bias field on a magneto-resistive layer of a magneto-resistive element, and a ferromagnetic underlayer which forms an underlayer with respect to the stabilizing bias layer, where the ferromagnetic underlayer is made of a FeCo alloy, a FeCoNi alloy or a FeNi alloy which is added with at least one element selected from a group of Pt, Pd, Ir, Rh, Ru and Au. According to the magneto-resistive head of the present invention, it is possible to reduce the head noise and obtain a satisfactory head characteristic, and to prevent undulations from being generated in the write head so as to prevent deterioration of the recording and reproducing characteristics, and it is possible to obtain a satisfactory hard magnetic characteristic.
A further object of the present invention is to provide a magnetic recording and reproducing apparatus, which includes any one of the magneto-resistive heads described above. According to the magnetic recording and reproducing apparatus of the present invention, it is possible to reduce the head noise and obtain a satisfactory head characteristic, and to prevent undulations from being generated in the write head so as to prevent deterioration of the recording and reproducing characteristics, and it is possible to obtain a satisfactory hard magnetic characteristic.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.